Question

Find the arithmetic mean an of an-1=3.9 and an+1=7.1

Answer 1

A[n] = (a[n-1] +a[n+1])/2 = (3.9 +7.1)/2 = 11/2 = 5.5

Answer 2

The arithmetic mean is 5.5

So therefor the answer is 5.5